<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <script src="https://cdn.jsdelivr.net/npm/vue"></script>
</head>
<body>
<div id="vue">
    <select v-model="selected">
        <option disabled value="">请选择</option>
        <option>A</option>
        <option>B</option>
        <option>C</option>
    </select>
    <span>选中的值: {{ selected }}</span>
</div>

<script type="text/javascript">
    var vm = new Vue({
        el: '#vue',
        data: {
            selected: ''
        }
    });
</script>
</body>
</html>